Patent Literature 1 discloses a Fabry-Perot interferometer including a substrate, a first mirror structure that has a lower fixed mirror disposed on the substrate, a second mirror structure that has an upper movable mirror facing the lower fixed mirror via a space, and a sacrificial layer that defines the space between the first mirror structure and the second mirror structure. In this Fabry-Perot interferometer, an outer surface of the sacrificial layer is exposed. In addition, the outer surface of the sacrificial layer exhibits a flat surface shape, is orthogonal to a surface on a side opposite to the first mirror structure in the sacrificial layer, and is flush with an outer surface of the second mirror structure.